Impact wrench having time lapse control valve

ABSTRACT

An impact wrench includes a compressed air inlet port having a valve operable with a control piece. An air passage has an exhaust port which is closed when the valve is open. A time lag valve is slidably arranged in a chamber between the air passage and an air passage communicating with the inlet port. A throttle valve regulating flow rate is positioned at an inlet port communicating with an air receiver.

United States Patent [191 Kotone June 26, 1973 IMPACT WRENCH HAVING TIME LAPSE CONTROL VALVE [75] Inventor: Eimatsu Kotone, Osaka, Japan [73] Assignee: Nippon Pneumatic Manufacturing Co., Ltd., Osaka-fu, Japan [22] Filed: June 30, 1971 21 Appl. No.: 158,226

[30] Foreign Application Priority Data July 20, 1970 Japan 45/72580 [52] [1.8. CI. 173/163, 91/38 [51] Int. Cl B25b 21/00 [58] Field of Search 91/38; 173/12, 163

[56] References Cited UNITED STATES PATENTS Yanchenko 91/38 X 3,336,840 8/1967 Alexander 91/38 Primary Examiner-Ernest R. Purser Attorney-E. F. Wenderoth et al.

[57] ABSTRACT An impact wrench includes a compressed air inlet port having a valve operable with a control piece. An air passage has an exhaust port which is closed when the valve is open. A time lag valve is slidably arranged in a chamber between the air passage and an air passage communicating with the inlet port. A throttle valve regulating flow rate is positioned at an inlet port communicating with an air receiver.

6 Claims, 2 Drawing Figures IMPACT WRENCH HAVING TIME LAPSE CONTROL VALVE This invention relates to an impact wrench using compressed air, particularly to an impact wrench in which a timer operable by compressed air is housed.

An impact wrench utilizing compressed air operates to rotate an air motor to drive the clamping head for a bolt or nut with the shaft of the air motor. And also, when clamping bolt or nut, a preset clamping torque must be maintained. Heretofore, a method has been used wherein the time interval from start of clamping necessary for reaching a fixed torque is set previously with a timer, and after lapse of the time interval, the air motor is automatically stopped, by the timer formerly, as the impact wrench and the timer have been disposed separately, the construction thereof has been such that the compressed air from the compressor was sent to the impact wrench through the timer thereby causing a defect during the installation thereof.

The first object of this invention is to simplify the installation by housing the timer in the impact wrench itself to eliminate the defect of the conventional impact wrench as above described.

The second object of this invention is to provide an impact wrench which is not bulky even when the timer is housed therein and also is simple in construction and easy to operate.

The third object of this invention is to provide an impact wrench in which is housed a timer, the set time of which is freely adjustable.

The objects above mentioned may be accomplished with the improvement, combination and operation of each part constituting this invention, and the detail thereof will be illustrated referring to the accompanying drawing and by the following detailed description.

Furthermore, the detailed shape and the modification of the construction of this invention are to be included in the claims described hereinafter.

FIG. 1 is a side view of the impact wrench according to this invention, the main portion of which is longitudinally sectioned.

FIG. 2 is an enlarged longitudinal section taken on the line 2 2 in FIG. 1.

This invention comprises an impact wrench body 11, a handle portion 12 at the rear thereof and a front case 13 fixed to the front of the body 11.

From the front end of the front case 13, projects the rotary shaft 14, and to the rotary shaft is fixed a tool head fittable the head of bolt or nut.

In the body 11 is disposed an air motor 15 of the well known vane type. In the front case 13 are arranged the transmission gear for transmitting rotation of the shaft of the air motor 15 to the rotary shaft 14 and a suitable pounding device for imparting high torque to the rotary shaft 14 when in use. For this pounding device, various well known devices are usable, and since this pounding device is not the principal part of this invention, it will not be described in detail.

16 is a trigger type control piece pivoted at the rear end of handle portion 12 by the shaft 17. This piece 16 contacts with its shoulder portion 20 the upper end of the slide rod 19 fitted slidably in the cylinder 18 fixed to the handle portion 12.

21 is the inlet port of compressed air provided to handle portion 12. To this inlet port 21 is connected a hose communicating with the source of compressed air.

22 is a valve port for communicating compressed air inlet port 21 and the air passage 23 in the handle portion 12. 24 is a valve for closing valve port 22 from the underside, and this valve 24 is pressed against the valve port 22 by the compression spring 25.

The lower end of slide rod 19 is fitted loosely in valve port 22 and abuts against the upper portion of the valve 24. Accordingly, when the valve 24 closes the valve port 22 by the compression spring, the upper end of the slide rod 19 slightly tilts the control piece 16 outwardly as shown in FIG. 1 by pushing upwardly the shoulder portion 20 of the control piece 16. When the outside of the upper end of the control piece 16 is pressed, the control piece 16 is turned round the shaft 17, the slide rod 19 is pressed down by the shoulder portion 20, the valve 24 is pushed down by the lower end of rod 19 against the elastic force of the compression spring 25 to open the valve port 22, and the compressed air inlet port 21 and the air passage 23 are placed in communication.

The middle portion of slide rod 19 has a reduced diameter portion 26, and at the upper and lower sides of cylinder 18 are formed a plurality of ports 27, 28. The upper ports 27 are communicated with the exhaust port 29 provided in the handle portion 12, and the lower ports 28 are communicated with the air passage 23. When slide rod 19 is rised and valve 24 closes the valve port 22, the ports 27, 28 communicate through reduced diameter portion 26 of the slide rod 19 to thereby communicate the air passage 23 with the open air through the exhaust port 29. And when the slide rod 19 is lowered and the valve 24 is separated from the valve port 22, the upper end of the reduced diameter portion 26 of the slide rod 19 is lowered below the upper ports 27, and ports 27 are closed by the upper periphery of the slide rod 19. Thus, air pasage 23 and the exhaust port 29 are not in communication.

In FIG. 2, 30 is the time lag valve chamber formed within a cylinder 31 in the handle portion 12. 32 is the time lag valve fitted slidably in the cylinder 31. To close one end of the valve chamber 30, this valve 32 is pressed toward the air pressure side by the compression spring disposed between the cover 33 fixed to the handle portion 12 with screws and the recess 34 formed in the spring side of the time lag valve 32. In this time lag valve 32 is formed also another recess 36 in the air pressure side, and at the middle of the periphery of the time lag valve 32 is formed the peripheral groove 37.

In opposite sides of the middle of the cylinder are formed the opening 38, one opening 38 communicates with air passage 23, the other opening 39 communicates with another air passage 40 formed in the handle portion. When the time lag valve 32 is pushed completely to the end of the air pressure side by the compression spring 35 as shown in FIG. 2, the peripheral groove 37 communicates the openings 38, 39, and when the time lag valve 32 compresses the compression spring and moves toward the cover 33, the openings 38, 39 are closed by the periphery of the time lag valve 32.

In cover 33 is formed an exhaust port 41, and at the end of valve 32 adjacent the recess 36 of is formed the further reduced diameter portion 42.

At the end of the cylinder on the air pressure side is formed the space 43 surrounding "the periphery of the reduced diameter portion 42. Space 43 communicates with the valve port of the check valve chamber 44 formed in the handle portion 12. In the valve chamber 44 is fitted the check valve 46 for closing the valve port 45 from valve chamber 44. Between check valve 46 and the screw plug 47 screwed in the end of a valve chamber 44 is disposed the compression spring 48 pressing the valve 46 against the valve port 45.

49 is a communicating passage for communicating the check valve chamber 44 and air passage 23. 50 is the communicating port for communicating a communicating port 49 and the opening 51 formed in cylinder 31 adjacent the space 43 end thereof.

In FIG. 1, 52 is an air receiver formed in the handle portion 12. This air receiver 52 is led to the air passage 23 through a communicating port 53. Also, the air receiver 52 and time lag valve chamber 30 on the side of the space 43 are communicated by another communicating port 54.

Communicating port 53, as shown in FIG. 2, communicates with the air passage 23 through the valve port 56 adapted to regulate the flow rate with the needle valve 55 as an example of a throttle valve. This needle valve 55 is screwed in threaded port 58 formed in the handle portion 12 with the malescrew thereof. The flow rate is regulated by turning the knob 59 disposed at the end of the needle valve 55 projecting through the outside of the handle portion 12.

At the outside of the knob 59 are formed plural recesses 60 spaced at intervals, and at a suitable position of the handle portion 12, the ball 63 engages one of the recesses 60 of the knob 59 by the elastic force of spring 62 disposed in the recess 61 formed to face a outside of the knob 59. Accordingly, when the knob 59 is turned, the ball 63 is pushed in the recess 61 by the periphery of the knob 59, and when the knob 59 is stoppedat a suitable point, the ball 63 tits in one of the recesses 60 of the knob 59 and thereby the knob 59 is locked,

In FIG. 1, 64 is an inlet port for the air motor 15, disposed in the body 11, 65 is an exhaust port, and 66 is a change-over valve for changing the direction of rotation. This change-over valve 66 is of a well known type wherein the flowing route of the compressed air supplied to the air motor 15 is changed 'by rotating the change-over valve 66 by a control piece 67 projected from a portion of the body 11 and thereby the direction of rotation of the rotor of the air motor 15 may be changed.

In aforesaid embodiment,as shown in FIG. 1, when the control piece 16 is not pushed, the valve 24 closes the valve port 22, so that the compressed air from the compressed air inlet port 21 will not flow into the air passage 23 and thus, the air motor 15 is at a standstill.

When the outside of the upper end of the control piece 16 is pushed with a finger or the like, then the shoulder 20 thereof pushes down the slide rod 19, and while the slide rod 19 closes communication between the exhaust port 29 and the air passage 23, the valve 24 is pushed down, and then the valve port 22 is opened, whereby the compressed air from the inlet port 21 enters the air passage 23 through the valve port 22, flows from the opening 38 through the peripheral groove 37 of the time lag valve 32 and also enters the air inlet port 64 from the opening 39 through the air passage 40, and after rotating the air motor 15, is exhausted from the exhaust port 65 through the change-over valve 66.

As above mentioned, when the compressed air flows into the air passage 23, a part of this air flows also into the air receiver 52 from the valve port 56 throttled by the needle valve 55 through the communicating port 53, and the air receiver 52 also communicates with the air pressure side in the time lag valve chamber 30 through communicating port 54. But since the flow rate of the air entering the air receiver 52 is limited by the needle valve 55, the air pressure in the air receiver 52 initially is considerably low.

Accordingly, as the pressing force of the time lag valve 32 due to the compression spring 35 is first large, the valve 32 maintains the condition shown in FIG. 2 and the air motor 15 continues to rotate, thereby clamping a bolt or nut with the clamping head fixed to the front end of the rotary shaft 14.

As the compressed air from the valve port 56 and the communicating port 53 flows into the air receiver 52 as above described, the air pressure in the air receiver 52 is increased gradually. As the air receiver 52 is communicated with the air pressure side of time lag valve chamber 30 through the communicating port 54, the air pressure in the recess 36 within the valve chamber 30 is increased gradually together with the air pressure in the air receiver 52, and'by this air pressure, the force pressing the time lag valve 32 against the compression spring 38 is increased gradually.

After lapse of a fixed time, pressing force of the valve 32 due to the air pressure in the recess 36 increases higher than the elastic force of the compression spring 35, and thereby the valve 32 moves toward the cover 33 while compressing the compression spring 35. Initially the valve 32 is risen gradually, but when the lower end of the valve 32 passes by the opening 51, the compressed air within the air passage 23 and the communicating ports 49, 50 flows rapidly from the opening 51 into the air pressure side within the valve chamber 30. Thereby, the air pressure pressing the time lag valve 32 is quickly increased, and the valve 32 is moved rapidly so far as to abut against the cover 33 while compressing the spring 35, so that the openings 38, 39 are closed by the valve 32, and communication between the air passages 23, 40 are shut off.

Accordingly, supply of the compressed air to the inlet port 64 is cut off and thereby the air motor 15 is stopped. When the control piece 16 is released after automatic stoppage of the air motor 15 'as above mentioned, the slide rod 19 and the control piece 16 are restored by the compression spring 25, the valve'port 22 is closed by the valve 24 and the air passage 23 is communicated with the exhaust port 29, so that the interior of the air passage 23 reaches atmospheric pressure, also the air pressure inthe airpressure side of the air receiver 52 and the time lag valve chamber 30 communicating therewith reaches atmospheric pressure and then the time lag valve 32 is pushed back by the compression spring 35. The air in the air pressure side of the valve chamber 30 initially escapes from the opening 51, but after the opening 51 is closed with the lower end of the valve 32, the air pressure within the valve chamber 30 is increased and opens the check valve 46. Thereafter the air escapes from the valve chamber 44 into the communicating port 49.

With the impact wrench according to this invention, the air motor 15 thereof is stopped automatically by the operation of the time lag valve 32 when a set time interval has elapsed after starting of the air motor 15 by pushing the control piece 16 as above described. The setting of the time interval for rotation of the air motor 15 may be accomplished by adjusting the needle valve 55 as a throttle valve with the knob 59 thereby regulating the amount of compressed air passing through the valve port 56. That is, as the amount of the compressed air passing through the valve port 56 is increased, the increase of the pressure in the air pressure side within the time lag valve chamber 30 is rapid, and thereby the time lag valve 32 acts early and stops the air motor 15. Thus, the set time interval may be short. When the amount of the air passing through the valve port 56 is reduced, the set time iriterval will become longer.

With this invention, since the time interval of rotation of the air motor may be set freely by rotation of the knob 5% and also since the timer is housed in the impact wrench, it is unnecessary to provide the timer separately. Although the timer is housed, the time lag valve 32 may be constructed compactly, and also the impact wrench itself may be constructed compactly by means such as utilizing the space within the handle portion 12 as the air receiver 52 and the like.

What I claim is:

1. A pneumatic impact wrench comprising:

a housing;

air motor means within said housing and having an operating shaft extending from said housing;

a main air passage in said housing;

an air inlet connectable to a source of compressed air in communication through an inlet port with said main air passage;

a control valve urged to close said inlet port and said communication between said main air passage and said air inlet;

an exhaust port to the atmosphere communicating with said main air passage;

control means for selectively moving said control valve away from said inlet port to open communication between said air inlet and said main air passage, said control means' including means for connecting said exhaust port'to said main air passage when said inlet port is closed and to close said exhaust port when said inlet port is open;

a time lag valve chamber in said housing;

a time lag valve slidably positioned in said time lag valve chamber and urged to a first end thereof;

opening means providing communication from said main air passage around said time lag valve to said air motor means when said time lag valve is urged to said first end of said time lag valve chamber, to thereby operate said air motor means;

an air receiver chamber in said housing;

first port means providing communication between said main air passage and said air receiver chamber;

selectively adjustable throttle means for restricting the size of said first port means;

second port means providing communication between said air receiver chamber and said first end of said time lag valve chamber;

whereby when air is supplied through said inlet port to said main air passage, a first portion of said air flows through said opening means to said air motor means, and a second portion of said air flows through said first port means, said air receiver chamber, and said second port means to said first end of said time lag valve chamber to urge said time lag valve to a second end of said time lag valve chamber;

said time lag valve having means for blocking said opening means when said time lag valve is moved to said second end of said time lag valve chamber, and thereby stop operation of said air motor means; and

communicating passage means providing communication between said main air passage and said time lag valve chamber adjacent said first end thereof but spaced a given distance therefrom, for providing rapid movement of air into said first end of said time lag valve chamber when said air is supplied to said main air passage after said time lag valve has moved said given distance toward said second end of said time lag valve chamber and for providing rapid exhaust of air from said time lag valve chamber through said exhaust port when said control means is moved to cause said control valve to block communication between said air inlet and said main air passage.

2. A pneumatic impact wrench as claimed in claim 1, wherein said control means comprises a trigger type control piece attached to said housing, and a slide rod extending into said housing, said slide rod having one end thereof engaging said control piece and the other end thereof engaging said control valve.

3. A pneumatic impact wrench as claimed in claim 2, wherein said means for connecting comprises a reduced diameter portion of said slide rod, said reduced diameter portion dimensioned to extend from said main air passage to said exhaust port when said control valve is closed.

4. A' pneumatic impact wrench as claimed in claim 1, wherein said time lag valve comprises a piston having longitudinal recess at the end thereof adjacent said first end of said time lag valve chamber.

5. A pneumatic impact wrench as claimed in claim 4, wherein said opening means comprises a groove extending around the outer periphery of said piston, and openings extending into said time lag valve chamber on oposite sides thereof.

6. A pneumatic impact wrench as claimed in claim 5, wherein said means for blocking comprises the outer peripheral surface of said piston between the end of said piston adjacentsaid first end of said time lag valve chamber and said groove. 

1. A pneumatic impact wrench comprising: a housing; air motor means within said housing and having an operating shaft extending from said housing; a main air passage in said housing; an air inlet connectable tO a source of compressed air in communication through an inlet port with said main air passage; a control valve urged to close said inlet port and said communication between said main air passage and said air inlet; an exhaust port to the atmosphere communicating with said main air passage; control means for selectively moving said control valve away from said inlet port to open communication between said air inlet and said main air passage, said control means including means for connecting said exhaust port to said main air passage when said inlet port is closed and to close said exhaust port when said inlet port is open; a time lag valve chamber in said housing; a time lag valve slidably positioned in said time lag valve chamber and urged to a first end thereof; opening means providing communication from said main air passage around said time lag valve to said air motor means when said time lag valve is urged to said first end of said time lag valve chamber, to thereby operate said air motor means; an air receiver chamber in said housing; first port means providing communication between said main air passage and said air receiver chamber; selectively adjustable throttle means for restricting the size of said first port means; second port means providing communication between said air receiver chamber and said first end of said time lag valve chamber; whereby when air is supplied through said inlet port to said main air passage, a first portion of said air flows through said opening means to said air motor means, and a second portion of said air flows through said first port means, said air receiver chamber, and said second port means to said first end of said time lag valve chamber to urge said time lag valve to a second end of said time lag valve chamber; said time lag valve having means for blocking said opening means when said time lag valve is moved to said second end of said time lag valve chamber, and thereby stop operation of said air motor means; and communicating passage means providing communication between said main air passage and said time lag valve chamber adjacent said first end thereof but spaced a given distance therefrom, for providing rapid movement of air into said first end of said time lag valve chamber when said air is supplied to said main air passage after said time lag valve has moved said given distance toward said second end of said time lag valve chamber and for providing rapid exhaust of air from said time lag valve chamber through said exhaust port when said control means is moved to cause said control valve to block communication between said air inlet and said main air passage.
 2. A pneumatic impact wrench as claimed in claim 1, wherein said control means comprises a trigger type control piece attached to said housing, and a slide rod extending into said housing, said slide rod having one end thereof engaging said control piece and the other end thereof engaging said control valve.
 3. A pneumatic impact wrench as claimed in claim 2, wherein said means for connecting comprises a reduced diameter portion of said slide rod, said reduced diameter portion dimensioned to extend from said main air passage to said exhaust port when said control valve is closed.
 4. A pneumatic impact wrench as claimed in claim 1, wherein said time lag valve comprises a piston having longitudinal recess at the end thereof adjacent said first end of said time lag valve chamber.
 5. A pneumatic impact wrench as claimed in claim 4, wherein said opening means comprises a groove extending around the outer periphery of said piston, and openings extending into said time lag valve chamber on oposite sides thereof.
 6. A pneumatic impact wrench as claimed in claim 5, wherein said means for blocking comprises the outer peripheral surface of said piston between the end of said piston adjacent said first end of said time lag valve chamber and said groove. 